maser .2 faa 
no.10) 


§cu9ud | Bulletin No. X 


oN 


- 


Rice - Publications of the University of Cincinnati, 
_ SERIES II. ) | 


The 


Crayfish of Missouri 


By 


Mary Steele. Hy 


The University Bulletins ate Issued Quarterly 


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- Entered at the Post Office at Cincinnati, Ohio, as second-class matter _ 


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UNIVERSITY OF CINCINNATI 


Bulletin No. X. 


Publications of the University of Cincinnati, 
‘Serigs II. Edited by HOWARD AYERS. Vor. II. 


The Crayfish of Missouri 


By MARY STEELE. 


The University Bulletins are Issued Monthly 


Entered at the Postofice at Cincinnati, Ohto, as second-class matter 


UNIVERSITY PRESS 


CINCINNATI, O. 


CONTENTS. 


Group I. 
C. blandingit. 
C. hay. 


Group II. 
C. gracilis. 


Group III. 


C. bartoniz. 
C. setosus. 


C. ayersit. 


Group IV. 

harrisontt. 
whitmant. 
rinmuUNtS. We 
rusticus. 

meatus. 

virilts. 


SES SFE 


General discusion of the species. 
Immature vzrzlzs. 
Variations within the species. 
First and second forms of the males. 
Summary. 

Biliography. 

S 3 Explanation of the Plates. 


INTRODUCTION. 


The variations found within a species has been asubject 
of interest among scientists from the earliest history of bio- 
logical sciences down to the present time. What it takes to 
constitute a species and at what point differences are impor- 
tant enough and constant enough to separate individuals in- 
to different species are still disputed questions. 

In my taxonomic studies upon the crayfish of Missouri, 
Dr. Ayers called attention to the fact that the species of 
Cambarus within this state presented favorable material for 
the study of variations and further that the field was the 
more attractive because so little work of this kind had been 
done in the Mississippi River basin. 

I have had an opportunity to examine a large number 
of individuals belonging to several species and have made a 
special study of the variations which a species presents. 
This has led me to conclude that, to say the least, it is 
very injudicious to name a species without having examined 
an abundance of material. 

There is too great a tendency to overlook variations 
within a species and to multiply constantly the number of 
species much to the confusion of our system of taxonomy. 
This consideration, together with the fact that little or no 
work has been done upon the fauna west of the Mississippi 
by those acquainted with the territory has led me to present 
this paper for publication. Practically all of the taxonomic 
work that has been done in this part of the United States 
has been done by men from the Kast who have made flying 
trips through the country and collected whatever specimens 
came in theirway. Generally they have not visited the terri- 
tory but have merely classified material sent them by 
collectors. 


(S) 


Usually the material sent them has been very meagre and 
the descriptions of habits and habitats has been very 
inadequate. 

In addition to the work already mentioned, I have also 
made a long series of observations upon the first and second 
forms of the males as found in C. virzlis, the results of which 
are included in this paper. 

During the observations many interesting points were 
suggested, for which I have as yet been unable to furnish 
any explanation; but which I hope to be able to further in- 
vestigate some time in the future. : 

J desire to express my indebtedness to Dr. Howard Ayers, 
for suggesting the general plan of the work and for constant 
advice and assistance. I am also under obligations to Dr. 
Chas. Thom, for material. ‘To Dr. Geo. Lefevre I am in- 
debted for a careful examination of the MS. 


THE CRAYFISH OF MISSOURI. 


When Dr. Faxon (85) published his “Revision of The 
Astacide, Part I. The Genera Cambarus and Astacus;” there 
had been reported from Missouri only seven species of cray- 
fish, all belonging to the genus Cambarus; C. blandingiz. 
Group I; C. diogenes, Group III; C. medius, C. rusticus, C. 
zmmunis, C. harrisoni and C. virilis Group IV. C. bartonzz, 
of Group III, was also included as probably occuring. 


These groups are the subdivisions of the genus Cam- 
barus, according to Faxon, who has divided the genus into 
five different groups, basing his division upon the number of 
hooked thoracic legs and the shape of the first pair of abdom- 
inal appendages of the male. 


The different species within the groups are distinguish- 
ed by minor and less constant differences than those which 
determine the group. Differences in the shape of rostruin, 
breadth of areola, shape and size of chela, whether spines are 
few or numerous on carapace and claws, and the general con- 
tour of body are some of the features that are takeninto con- 
sideration in determining to what species an individual cray- 
fish belongs. iG 


(6) 


Since Faxon’s paper was pttblished several other species 
have been identified as native to Missouri. Among these 
may be mentioned, C. hayz, Group I; C. gracilis, Group II; 
C. setosus, Group III, and C. ayerszz, Group III. ‘The last 
two are blind species. C. ayerszz is now described for the 
first time, and C. se¢osus, was classified and named by Faxon 
(89) and has as yet been reported from no other state. 


Faxon has divided the territory occupied by the different 
species of Cambarus into two provinces, a southern and a 
northern one. ‘The southern province embraces the Atlan- 
tic States south of North Carolina, the Gulf States and Cuba, 
and is characterized by the prevalence of species belonging 
to Groups I and II. The northern province includes the 
Atlantic States north of South Carolina, the Mississippi Val- 
ley States north of the Gulf Statesand Canada. In this pro- 
vince, forms of Group III and IV are dominant. However, 
species of Groups I and IJ are found in this province, and 
likewise species of Groups III and IV are found in the 
southern province. In fact there are five species from Group 
Ill, C. acuminatus, C. latimus, C. extranus, C. gtrardianus 
and C. jordani, and also three species from Group IV, C. ala- 
bamensis, C. compressus and C. shinosus that Faxon considers 
as restricted to the southern province. Only two species 
of Group I, C. dlandingii and C. pellucidus and two species 
of Group II, C. stmulans and C. gracilis had been reported 
from the northern province when Faxon published his paper. 
However, within the last three or four years there has been 
collected within this state another member of Group I, C. 
hayit and also a member of Group II, C. gracilis. 


Heretofore C. hayi had been reported from but one state, 
Mississippi. Doutless other species seemingly restricted to 
the southern province would also be found in the northern 
if the territory were carefully searched; but the species 
which are found in Missouri centainly bear witness to Fax- 
on’s statement that Groups III and IV dominate in the north- 
ern province; for of twelve species that have been identified 
as certainly native of Missouri six species belong to Group 
IV and three to Group III, leaving but three species as mem- 
bers of Groups I and II. 


(7) 


GROUP I. 


Beginning with the members of Group I, I shall give a 
somewhat detailed account of the species of Cambarus 
found in Missouri, without going into a systematic des- 
cription of any except new species. So far only two mem- 
bers of Group I have been found in the state; C. blandingii 
var. acuta and C. hayt. 


CAMBARUS BLANDINGII VAR. ACUTA, Faxon. 


Under the head of C. dlandingii (Harlan) Faxon (oc. cit. 
p. 19) has included a number of species decribed by other 
authors as synonyms of this species. Faxon also forms a 
variety (C. blandingii var. acuta) under this species and in- 
cludes under the variety a number of species and varieties 
of other authors Coc. cit. p. 20.) ‘This variety of C. dland- 
ingit occurs in Missouri but has been reported from but one 
locality, St. Louis. As to whether this species as found in 
Missouri shows any peculiarities I cannot say for the only 
specimens in the collection here came from Indiana. 

Faxon says that the individuals of this species which are 
collected in the Western States differ considerably from those 
collected in the Southern States, and he considers the differ- 
ences of the Western species from the Southern, characteris- 
tic enough to form of the Western species a stb-variety 
under C. blandingii var. acuta. 


CAMBARUS HAYI, axon. 


C. hayt, as was mentioned above had only been reported 
from Mississippi until April 10, 1897 when this spccies was 
taken from James River, Mo. C. hayz is very clocely related 
to C. dblandingii but is easily distinguished from it by the 
first.pair of abdominal appendages of the male, the deeply 
excavated rostrum and the shorter antennal scales. 

Since C. hayz is not known except from two states and 
only a few individuals have ever been taken, it would appear 
that the species is not at all prolific. However, individuals 
attain a very considerable size. The following are the 
measurements of a first form, male. Length from tip of ros- 


(8) 


trum to tip of telson 113 mm.; length of carapace 56 mm.; 
width of carapace 33 mm.; length of hand 67 mm.; length of 
movable finger 36 mim. 


GROUP II. 


CAMBARUS GRACILIS, Bundy. 
Plate III—Fig A,, to A; and B, to Bg. 

Only one species of Group II, C. gracilis, has been re- 
ported from Missouri, and all specimens found belong to the 
collection here. Most of them were found in the vicinity of 
Columbia, although specimens have been taken near Mexico, 
Audrain County. 

C, gracilis, is one of the burrowing species and is seldom 
found except during February and March. ‘Then the fe- 
males come from their burrows along the banks of creeks and 
ponds, ont into the water with their newly hatched young. 
By the latter part of March the adults have returned to 
their burrows. ‘The young however may still be found in 
the open water during April and May. 

Faxon mentioned that among the hundreds collected 
along the water-courses in the spring time, but few males 
have been found. ‘The same is true of the collection here. 
From sixty-two adult specimens collected March 10, 1897, 
only two are males, the larger of these being but 69 mm. in 
length. Among the adult specimens taken in this vicinity 
March 1899 not a single male was found. ‘The collection 
taken last spring, March 1900, contained no males. 

However, this does not hold true for small specimens, for 
out of fifty-two of the young, 25-35 mm. long, taken at the 
Same time and place as the sixty-two adult specimens, twenty- 
seven were males and twenty-five were females. Also among 
the young individuals collected in March 1899, I find as 
many males as females. ‘The same is also true of the collec- 
tion for 1900. ‘This shows that while they are young, males 
’ are as plentiful as females and come from the burrows in as 
great numbers. 

Although C. gracilis is seldom found except in early 
spring, I once found a solitary adult female in July, crawl- 
_ ing across a clayey road just after a heavy rain. A solitary 
adult male about 50 mm. in length was found at Columbia, 


(9) 


under a log in June 1897. Last summer August 1899, I capt- 
ured two males in their burrows. "The burrows were out 
on the open prairie some distance from any stream. 
Those that I investigated were along a new road that was 
being graded. One of the workmen who happened to know 
of my interest in crayfish noticed the burrows and told me of 
them. He also said that the crayfish worked at night, for 
during the day the burrows were plowed over and their open- 
ings stopped, but in the morning when he came out to work 
the same holes were again opened up and surrounded by a 
small heap of fresh earth. I determined to visit the burrows 
myself. Accordingly, accompanied by my father and the 
workman who had told me of them, I visited the burrows be- 
tween eight and nine o’clock P. M., although many of the 
burrows were found, in none of them did I find a crayfish 
at work. It was decided to dig some of the burrows out. 
The burrows descended vertically into the ground for about 
four feet; the main tunnel varying from an inch to an inch 
anda halfin diameter. ‘The tunnel was terminated by a 
flask-shaped enlargement, the greatest diameter of which 
was about six inches. ‘This enlargement was partially filled 
with mud and water. 


Several burrows were dug out, but only two contained 
crayfish, one in each. From one we took a male, and from 
the other a female, each about 55 mm. in length. If the 
crayfish came out at night, we must have been too early for 
them, and since the earth which the workman found around 
the mouth of the burrow in the morning was still moist, it 
seems probable that they do their work towards morning. 


C. gracilis has much the general form of C. dzogenes of 
the same region, except that it is smaller. T‘he male appen- 
dages differ considerably from those of C. diogenes; also the 
annulus ventralis is quite different in the females of the two 
species. In C. gracilis the annulus is movable and is dentic- 
ulate on the anterior border, while in C. diogenes the annu- 
lus ventralis is bounded anteriorly by two blunt tubercles. 
Besides, the female C. gracilis lacks the battered appearance 
that is characteristic of the old specimens of the female C. 
diogenes. ‘These differences easily distinguish the females 
of the two species which are often found in company. 


(10) 


C. gracilis does not attain as great a size as many other 
species of Cambarus. ‘The largest C. gracilis I have ever 
seen does not exceed 82 mm, while it is not at all unusual to 
see C. wzrilis and \S. diogenes 120 mm. long. 


The females differ from the males in having a shorter 
hand and broader abdomen. A male of 69 mm. has a hand 30 
mm. long and 12 wide, while a female of 82 mm. has a hand 
only 27 mm. long and 11 mm.wide. 


Very little variation is to be noticed among adult indi- 
viduals of C. gracilis. 'This may be due in part tothe scar- 
city of the male specimens for in all species the males show 
much greater variation than the females. ‘The fact that this 
is a burrowing species and consequently less subject to vary- 
ing conditions than crayfish that do not burrow may to some 
extent explain their uniformity of parts. Evenincollections 
of immature forms where males are numerous there is found 
mutch less variation than among individuals of the same 
age belonging to other species. C.virilis for instance, a 
species which shows much individual variation. 


As is well known, the young Cambarus of any species 
differs much insome ofits partsfrom the adult forms. Ihave 
had no opportunity to examine C. gracilis less than 7 mm. 
in length; but individuals 7 or 8 mm. long show varations in 
breadth of areola and length and shape of rostrum. At this 
age the rostrum is still short and bent down between the 
eyes, as in the case with all newly hatched crayfish. How- 
ever, in adult C. gracilis the rostrum is short as compared 
with most species of Cambarus, and is bent downward be- 
tween the eyes so that it fits closely over the antennules. I 
attribute this form of rostrum to the burrowing habits of the 
species. 


specimens of C. gracilis 28-35 mm. long are but little 
different from mature forms, so far as general appearance 
- goes, but careful observation shows an important variation 
from the adults in both males and females. ‘The annulus 
ventralis is not denticulate on the anterior border, nor does it 
have the characteristic appearance from behind of two inter- 
locked crescents; it is also much less grooved and convoluted 
than in the adult female. In the adult males of this size, 


(11) 


30-35 mm., the first pair of abdominal appendages are slen- 
der and unarmed much as one would expect to find second- 
form adult males; but Faxon says he has never seen a second- 
form male C. gracilis, and from what I can learn none have 
ever been reported. ‘The antennal scale in the young indi- 
viduals is relatively broader and is truncate at the apex, and 
also has the apical spine much shorter than in the adult. 
Upon measurement there is found to be some variations in 
relative lengths of cephalothorax and abdomen, although 
not nearly so much as C. vz7z/s shows. 

Below are measurements in mm., of twelve individuals; 
the first column giving length of the body, the second, 
length of abdomen, and the third length of cepalothorax. 


BODY. ABDOMEN. CEPHALOTHORAX. 


32.5 mm. 16.5 mim. 15.0 mm. 


TALC kh TOOL LION 
30,0). \ 15.0 ‘ SO 0a 
SO ies ICS OMNI ase Oey 
BS Onin ZS Le 
BOLO PSLOe ie TSO 
BOO ith 15258 LEMS Me 
DE Sy ink SVOnn iG DOCS NL OH 
2S eal hteas irene ACO wey 
SILO TGGO Wi 15000 i 
B35) 17) GES nins ZO 
B20 es TSS MA 1625) Hi 


In noticing these varations it will be seen that the length 
of the cephalothorax and abdomen is equal in some cases, 
but that in the majority of cases the abdomen is longer than 
the cephalothorax. Now there is also a variation in these 
relative lengths in adult specimens, but instead of the abdo- 
men in most cases being equal to or greater in length than 
the cephalothorax the reverse is the case; as may be seen in 


(12) 


the appended columns of measurements of the mature gracilis. 


BODY. ABDOMEN. CE PHALOTHORAX. 
70.0 mm 35.0 mm 35.0 mm. 
BAO DS On QOIOW ar 
55.0 “ ZOE 26:0 
FOO) SOON! AO Oi 
Sea Ns DOO DOES Wis 
BOs" DAN Sa, 25.5 °° 
GiON ZO USN" BOER in, 
Eye Rca’ ZOO Dorey itt 
VETO ONS BR OM 40.0 ‘' 
69.0 “° BAO 35.0 “ 


Faxon (loc. cit. p. 57) describes g. gracilis as having 
the abdomen shorter than the cephalothorax by the length 
of the rostrum, but this cannot be said of the specimens 
which I have at mycommand. Although amajority of those 
measured show an abdomen shorter than the cephalothorax, 
in most cases the cephalothorax does not exceed the abdomen 
more than from 0.5 to 1.5 mm., which is not so much as half 
the length of the rostrum of a mature C. gracilis. 

I have not yet been able to decide fully at what age and 
size C. gracilis becomes mature. But since the first pair of 
abdominal appendages of the male and the annulus ventralis 
of the female both have characteristic forms in the adults 
which are quite different from the form of these organs in 
the immature individuals, it occured to me that a graded ser- 
ies of these appendages might be useful in determining the 
maturity of individuals. It may alsoserve as a guard against 
mistakes in classification, for if only immature forms of a 
species are at hand one may class them as mature individuals 
of a different species. | 

Plate III,—Figs.—A, to A; show a graded series of the 
first pair of abdominal appendages of the male. Fig. A, is 
taken from a crayfish only 23 mm. long. ‘These appendages 
show very little modification from the typical abdominal 
appendage. Figs. A, and A; show an increased modification, 
and by the time the crayfish is 40 mm. in length the appen- 
dages have become modified asin Fig A,. ‘The crayfish may 


(13) 


be adult at this stage. I have found females very little 
larger, that werein berry. Fig. A; shows the appedages from 
a male 67 mm. long. Sofar as Ihave been able to observe, 
this figure represents the typical appearance of this pair of 
appendages in the large male C. gracilis. 

Plate III, B, to Bg show the modifications through which 
the annulus ventrails passes during the growth of the female 
C. gracilis. Fig. B, drawn from a specimen 20 mm. long, is 
very simply formed, and the central depression is very slight. 
The complexity of structure and increase in depth of central 
depression gradualy increases with the age and size of the 
animal, until the annulus ventralis of the larger females (Figs. 
B, and B,) presents a very complicated and characteristic 
structure. Figs. B,., as stated above, is taken from a spec- 
imen 20 mm. in length; Fig. B, from one 22 mm.; Fig. Bg, 
27.5 mm.; Fig B,, 30 mm; Fig. Bs, 35mm.; Fig. B,, 36mm.; 
Fig. B,, 50 mm.; and Fig. B, 60 mm. 

I think that Figs. B, and B, can both properly be 
regarded as belonging to adult individuals, for I have found 
females of C. gracilis not exceeding 40 mm. that were in berry. 

However, Fig. B, can be considered the more typical form 
of the adult annulus ventralis of the female C. gracilis. 

One other point should perhaps be mentioned before 
leaving the consideration of this species. ‘That is concerning 
their moulting season, which so far I have been unable to 
determine. 


As is well known young crayfish of any species have no 

particular, well-defined moulting season, but may moult at 
almost any time during the year. ‘This is no less true of C. 
f£racilis than of other species. However, of the adult forms 
I have been entirely unable to find one moulting at any 
period whatever. 
It is impossible that the moult should have taken place 
before the spring collections were made, for often the females 
that were captured had the newly hatched young still 
clinging to the swimmerets. Besides, amoung those that 
carried no young there was no sign of a recent moult. 


[have kept them through the summer and far into the 
following winter without a molt occuring. ‘The specimens 
mentioned above which were taken from their burrows in 


(14) 


August, were kept through the fall, winter and the following 
spring, when they died without having moulted. 

C. gracilis has been under observation at all seasons of the 
year, but I have not seen one over 30 mm. in length pass 
through a moult. Laboratory conditions might retard their 
moulting, but it is improbable that these conditions should pre- 
vent moulting. C. gracilis thrives under laboratory treatment, 
and is hardier and more easily kept alive than some other 
species. 

In experimental work on the appendages of crayfish I 
found the young of C. gracilis to grow more rapidly and with- 
stand mutilation as well if not better than the young of C. wirilis. 


GROUP III. 
CAMBARUS BARTONII, GIRARD. 


For synonymy see Faxon (loc. cit. pp. 59, 60.) 


Faxon (loc. cit. p. 61) mentioned C. barton as probably 
belonging to Missouri, but, although several new species have 
been discovered in the state since that date, this species has not 
been found. . 

C. vartonu is taken as a type of Group III. It has a wide 
geographical distribution, and, as might be expected, is subject 
to much variation. These variations affect especially the 
rostrum, chele, areola, antennal scales and epistoma. In the 
common Eastern form the rostrum is short, broad, and almost 
plane above, the sides nearly parallel from the base almost to 
the tip, where they suddenly converge to form the short 
acumen. ‘The chelz are coarsely punctate, the inner margin of 
the hand sub-tuberculate, and the fingers gaping at the base. 
The areola is quite narrow, and the antennal scale is narrow. 

The Western specimens have a longer, narrower rostrum, 
the margins of which converge gradually to form a longer 
acumen. ‘The areola is wider, and the antennal scale broader 
at the base. ‘The chele are smoother and in some individuals 
bearded at the base. 

Although the extreme Western forms differ much from the 
extreme Eastern, there are so many intermediate gradations 
between them that Faxon does not consider it justifiable to 
classify these extremes as different species. 

C. bartona is the only eyed species that is known to inhabit 
Mammoth Cave. It is found there in company with a blind 


(15) 


species, C. pellucidus, a member of Group I. Some writers have 
been led to conclude, by finding C. bartonu in company with the 
blind species, that C. peliucidus has been directly derived from 
C. bartonti, but Faxon, after a careful comparison of likenesses 
and differences of the species, and in consideration of the fact 
that the general characteristics of C. pellucidus (Tellk.) place it 
in Group I., suggests that it is probable that the origin of the 
blind species dates much farther back than would be possible 
were it derived from C. bartonti. He says (loc. cit. p. 42): “ The 
simple form of the male appendages and the combination of 
characteristics belonging to different groups seen in C. pellucidus 
indicate to my mind that it is a very ancient form, which has 
been preserved in the seclusion of the cave while its nearest 
kin succumbed to the sharper struggle incident to life outside, 
or were replaced by modified descendants evolved to meet the 
changeable conditions which obtain without the caverns. This 
view is rendered more probable when one remembers that this 
same blind form C. pellucidus occurs in the Wyandotte Cave on 
the other side of that ancient river, the Ohio. The transpor- 
tation of an eyeless species from the Kentucky caverns to those 
of Indiana seems out of the question, and one is driven to the 
conclusion that the subterranean waters of both localities 
derived this eyeless species from a simpler form with well- 
developed eyes, that peopled the streams throughout this region 
at a remote period.” 


_CAMBARUS SETOSUS, FAXON. 


Although C. bartonu and C. pellucidus can not be regarded 
as Closely allied species, there are two blind species of the 
Bartonii Group for which a close relationship can be claimed. 
These are C. hamulatus and C. setosus. ‘The latter has been 
reported from Jasper County, Missouri, but from no other 
locality. It was first named and described by Faxon (’89). 
Miss Ruth Hoppin collected this species from Wilson’s Cave 
and wells in the central part of Jasper County. Samuel Gar- 
man (89) quotes from letters of Miss Hoppin a description of 
the wells and cave. I reproduce a part of the description here: 

“The cave is about fifty feet long and nearly as wide, oven- 
shaped and high enough to stand in, except around the sides. 
* * * A small, very clean stream flowed along the left side, 
having a width of two feet and a depth of three, with tempera- 
ture of plus 54°F. About ten feet from the entrance the light 


(16 ) 


struck the stream in such a manner that we could see everything 
in the water without a lantern. The first things that caught 
the eye were a lot of crayfish, a dozen in all, like those I took 
from the wells. It seemed as if I might take every one of them. 
But though blind they have one or more of the other senses 
very keenly developed. J am very sure that they, as well as 
the white fishes, have the tactile sense developed to an unusual 
degree. At the least touch upon the water they dart away. 
* * * The crayfish were all found near the entrance, where 
Biene ts) consideraple light,.* '*)* 1. concluded that ithe 
crayfish liked the light. Perhaps they remain near the entrance 
because there they find a supplv of food. From one well thir- 
teen blind crayfish were taken, from another two, and from 
ameter one, ~ 7 * One well, an artesian, went dry when 
a neighbor dug another farther down the hill. It was found 
that the first well opened at the side directly into a small cave. 
All these are in limestone; only in this formation is good water 
to be obtained hereabout. The larger caves in this vicinity are 
under the limestone cliffs and hills that skirt Centre Creek. 
The wells are usually walled with stones that leave spaces 
through which the fishes may pass. There are probably many 
small subterranean springs and streams, not one underlying 
lake, as popular belief has it.” 


Garman (loc. cit. p. 231) says of these caves that “It is 
evident from the notes that these caves are numerous and sim- 
ilar to those in the same formation in other states.” 


Besides the cravfish, several other species of animals were 
found in the caves and wells, and Garman feels sure that further 
collecting will reveal several other interesting forms. Of the 
Crustacea he says (p. 235): “In part, at least, the problem of 
the origin of the cave crustacea is simplified by the fact that 
they are so distinct in various caves as to leave no doubt that 
they are descended from ancestors already of different species 
at the time of entering subterranean habitations. The blind 
crayfish of the Missouri caves is very distinct from any previ- 
ously known; it is described under the name Cambarus setosus. 
The common species of the neighborhood, C. virilis, is also 
found to enter the underground retreats, but it is not of the 
outside forms, the nearest ally of the blind form. ‘The latter 
bears so close an affinity to C. barton as to suggest derivation 
from it. A somewhat parallel condition exists in the caves of 
Missouri and those of Kentucky. In these last, with the blind 


(17) 


C. pellucidus we find C. bartonu, the nearest ally of the blind cray- 
fish in Missouri, C. setosus, and with the latter again in the 
Missouri caves is found an eyed species, C. vwirilis, more nearly 
allied to the blind one in the Mammoth Cave. The relationship 
existing between the species C. setosus and C. barionu is much 
closer than between C. pellucidus and C. virilis. A distribution 
of C. bartoni: covering so large a portion of the Upper Missis- 
sippi Valley to some extent favors the idea of the derivation 
from it of C. setosus. The greater difference between C. pellucidus 
and all known eyed species points towards a longer subjection 
of that form to the spelzan influences.” 

C. hamulatus (Cope, Faxon), the blind species from Nicka- 
jack Cave, Tennessee, stands between C. setosus and C. pellucidus, 
but nearer to C. setosus. C. hamulatus, however, does not occur 
in Missouri. 


CAMBARUS AYERSII, N. SP. 


Plate Vision 


In 1897 Dr. Howard Ayers found in the stream in Fisher’s 
Cave, near Springfield, Missouri, a species of blind crayfish 
which belongs to the C. bartonu group, and in some respects 
reseinbles C. setosus very closely, yet it differs much in others. 
On account of these differences it is here described as a new 
species. 

Male, form IT. — Rostrum medium length, shorter than the 
antennal scales, slightly concave above, with short acute lateral 
spines; acumen triangular, acute. Postorbital ridges short, 
terminated by an acute spine. Carapace subcylindrical, flat- 
tened and smooth above; portion of carapace behind cervical 
groove very long; sides of carapace behind cervical groove 
coarsely granulate, in front of cervical groove finely spinulate; 
branchiostegian spine short, acute, antennz slender and longer 
than the body. Hand long and slender, inner border orna- 
mented with a row of small, sharp tubercles. Carpus slender, 
with deep indentation on dorsal surface, inner margin with four 
sharp .spines, lower surface with two sharp spines. Upper 
margin of the meros subdentate, lower surface of meros fur- 
nished with sharp spinules arranged bi-serially. Upper surface 
of the basal segments of the antennules ornamented by tufts of 
rather long sete. Third pair of legs hooked. First pair of 
abdominal appendages fashioned after the type of C. bartonii 
Group; short, articulated at the base, dilated in the middle; 


(18) 


tips bifid, ending in two short recurved corneous hooks which 
are closely approximated, the outer hook being visible from the 
median aspect, tip of the inner hook slightly attenuated. A few 
fine seta are scattered on the dorsal aspect of the abdomen. 

Measurements of Male, form II. — Length from tip of ros- 
trum to posterior border of telson, 66 mm.; length of cephalo- 
thorax, 32 mm.; length of abdomen, 34 mm.; length of rostrum, 
45 mm.; length of antennz from base of antennal scale to tip, 
89 mm.; length of hand, 32 mm.; breadth of hand, 9 mm. 

The chief differences between this species and C. setosus lie 
in the presence of postorbital ridges, postorbital spines and 
rostral spines, which are well developed in these specimens, 
while they are described as absent in C. setosus; also in the 
breadth of areola. CC. setosus is described as having a narrow 
areola, while in this species it is strictly linear. Then again, 
the first pair of abdominal appendages are not like those 
@esenbed tor ©. sefosus. Garman (loc. cit. Pl. I.) figures and 
describes the first pair of abdominal appendages of the male 
C. setosus, and, although he figures three different forms that 
these appendages may take, none of them correspond to the 
form of appendage found on the species C. ayersu. 

From the figures and description of Garman it is certain 
that this species is not C. setosus. 

Since writing the above I have received from Dr. C. Thom 
a small (31 mm. in length) living specimen of blind crayfish 
which was taken from a well sixty feet in depth at Joplin, Mis- 
souri. It is not unusual to find these blind crayfish in that 
vicinity. 

It had been kept a week or two before I was able to make 
observations on its behavior in confinement. I can get no 
evidence that the rudimentary eyes are sensitive to light or are 
more sensitive to touch than other parts of the body. When 
placed in a glass jar with paper on one side it hides on the shady 
side. This crayfish lived but a short time, and was not active 
in captivity. It was almost colorless, and the carapace was 
translucent. Wilson’s Cave, where C. sefosus is found, is not 
more than fifteen or twenty miles from Joplin. 

In many respects this specimen accords with the descrip- 
tion of C. setosus. In others it differs from C. setosus, yet not 
more than could be accounted for by its small size and the fact 
that itis afemale. As is well known, even among eyed crayfish 
the females alone are not sufficient to satisfactorily determine 
a species. 


(19) 


C. setosus is described as having antennz as long or longer 
than the body. In this specimen they are considerably shorter. 
The chelz have very much the general shape described for 
C. setosus, but are scarcely spiny at all, and are less) seteses 
Again, the areola could not well be described as narrow, for it 
is of medium width; but this may be due to its being a young 
specimen, for the areola in immature crayfish is proportion- 
ately broader than in adults. 

Miss Hoppin states that among living specimens the young 
C. setosus are not so white as the older ones, and she also says 
that the specimens became opaque when placed in alcohol, 
although in life they are so transparent that the movements of 
the internal organs can be seen. In this specimen, which has 
now been in alcohol five months, I can not see that its color or 
transparency has been materially altered from what it was in 
life. ‘The part of the carapace in front of the cervical groove 
is still so transparent that, with a magnification of ten diameters, 
the fibers of the gastric muscles and the coeca of the hepatic 
gland can readily be seen. 

This specimen differs still mcre from C. ayersii than from 
C. setosus. The general contour of the body resembles that of 
C. ayersi, but the relative lengths of the abdomen and cephalo- 
thorax differ more, the abdomen being 3 mm longer tian 
cephalothorax, while in C. ayersw it is only 2 mm. longer. 
Again, in C. ayersw the antennz are much longer than the body, 
while in this specimen they are not so long. ‘The hand is not 
spiny, and only very sparsely setose. The carpus is without 
the conspicuous indentation on its dorsal surface found in 
C. ayersii, and has hut one spine on the lower surface and one 
on the inner border. The lower border of the meros has a 
double row of very fine spinules. The rostrum is more concave 
than in C. ayersu. and the rudimentary eyes less completely 
hidden underneath it. The antennal scales are longer than the 
rostrum. 

Altogether, I consider that this small specimen shows more 
points in favor of C. sefosus than in favor of C. ayersit. 


CAMBARUS DIOGENES, GIRARD. 
Kor synonymy, see axon (80, p.) 71). 


This species has a widespread distribution over the United 
States. It extends north to the Great Lakes, south to the 
Gulf, east to the Atlantic coast and west to the Rocky Moun- 


(20) 


tains. In Missouri it has been found in Carroll, Boone and 
St. Louis Counties. In the general form of its body and in its 
habits it resembles C. gracilis, and is often collected in company 
with this species. In one collection are five crayfish taken at 
the same time from Rollin’s Pond, near Columbia. Of these 
five specimens, two are large first-form males of C. diogenes; 
the other three are medium-sized females of C. gracilis. Unlike 
the males of C. gracilis, the males of C. diogenes are found in as 
great abundance as the females. 

In discussing C. gracilis I have mentioned the resemblances 
between these two species. Specimens of C. diogenes from the 
same locality vary much. In some the rostrum is deeply exca- 
vated. The rostrum of the females is bent down at a greater 
angle than the rostrum of the males. In the females the abdo- 
men is noticeably broader and flatter than in the males. This 
is true to some extent of all species, but it is more pronounced 
in C. diogenes than in any species I have studied. 

Faxon says the Western specimens are larger than the 
Eastern ones. He also notes other differences between the 
Eastern and Western specimens. In individuals from the East 
the areola is not completely linear, the rostrum is narrower, and 
the epistoma narrower than in individuals from the West. He 
considers these specimens sufficiently different from the West- 
ern form to be classed as a variety, and he calls them C. diogenes, 
ludoviciana. 

C. diogenes is pre-eminently a burrowing species. It is 
often found at a great distance from surface water, as in stream, 
in meadows and cornfields. 

Several accounts of their burrows and mud chimneys have 
been written. Audubon (44) is the first to figure and describe 
the mud chimneys built by C. diogenes. His description of them 
is in connection with his description of the ingenious manner in 
which the White Ibis draws the crayfish from its hiding place. 

Girard (52) has also given an account of their burrows and 
chimneys. His observations were made in the vicinity of Wash- 
ington, D. C. A part of his description I quote here: “The 
holes as they appear at the surface of the ground are nearly 
circular, and vary from seven-tenths of an inch to an inch and 
a half in diameter. The depth of the burrows varies with the 
location; these we generally found to be from sixteen inches to 
two feet, and sometimes to three feet and more. * * * 
From the surface of the ground the excavation exhibits a 
gradual slope, in direction more or less undulating, for a dis- 


(21) 


tance from five to ten inches, when it becomes vertical for 
six or eight inches, and then terminates in a sudden bottle- 
shaped enlargement, in which the animal is found. The bottom 
of the burrow having no subterranean communication, no other 
issue except towards the surface, it is entirely isolated from its 
neighbors and leaves no chance for escape to its inhabitants. 
The same burrow may have several external holes connected 
with it, several inclined channels, which, however, meet at the 
depth where it becomes vertical. We found constantly the 
cavity full of water, but this was in March and April. The 
bottom for several inches was filled with soft, pulpy mud. 

“There are other instances of burrows somewhat more 
complex. Their direction may be oblique throughout their 
whole extent, and composed of a series of chambers or ovoid 
enlargements succeeding each other at short intervals. Some- 
times, also, and connected with one of the chambers, a narrow 
and nearly tubuliform channel extends downward to a much 
greater depth, and appears to us as a retreat either during the 
cold winter or else during the dryness of summer, when the 
water is low. ‘That it is not for the mere purpose of escaping 
pursuit we infer from the fact that we repeatedly caught the 
animals in the chambers above, where they remained quietly 
instead of attempting to disappear into the compartments below. 

x x : 2 * *k “x x 

“Tn the spring, and, we are told, in the fall also, the burrow- 
ing crayfish builds over the holes of its burrow a chimney of the 
maximum height of one foot, but most generally lower. The 
chimney, circular-pyramidal in shape, is constructed of lumps of 
mud varying in size, irregularly rolled up and piled up, one upon 
each other, and intimately cemented together. Its exterior 
has a rough and irregular appearance, whilst the interior is 
smooth and as uniform as the subterranean channel having the 
same diameter.” | 

Girard stated that the crayfish worked at night, but that he 
had never been able to see the animal at work. However, since 
that time Dr. Abbot (’95) has published a paper in which he 
states that his nephew, Mr. Joseph De B. Abbot, has seen the 
crayfish engaged in building its chimney. The observation was 
made at night by the light of a candle. The crayfish was seen 
to emerge partially from its burrow, bearing “on the back of 
its right claw a ball of clay mud which, by a dextrous tilt of the 
claw, was placed on the rim of the chimney.” Then the crayfish 
remained perfectly quiet for a few seconds, when it suddenly 


(22) 


doubled up and dropped to the bottom of the burrow. There 
elapsed some three or four minutes between each appearance, 
but every time it came it brought a ball of clay and deposited 
it in the manner I have described. About two-fifths of the balls 
were not placed with sufficient care, and rolled down the outside 
of the chimney.” 

Besides the descriptions of the habits of these burrowing 
crayfish which I have already quoted, I may also mention 
papers by R. S. Tarr (84) and Dr. C. C. Abbot (84). 

Tarr believes that the chimneys are merely the result of the 
excavation of the burrows, a sort of accidental accompaniment, 
and imply no design on the part of the crayfish. On the other 
hand, Dr. Abbot believes them to be due to a definite and care- 
fully executed purpose on the part of their architects. They 
are often built on the steep banks of ditches, where the ejected 
mud would surely roll into the ditch if not carefully arranged 
to prevent it. In several instances observed by Dr. Abbot, 
where the chimneys were built on sloping banks, the base of 
the chimney was provided for by leveling the ground before 
the foundation of pellets of mud was laid. From observations 
made on forty of these towers or chimneys, Dr. Abbot is con- 
vinced that not one of the forty could be the result of accident. 

From the observations made up to this time, no one has 
been able to give a satisfactory explanation as to the object in 
building these elaborate burrows and the seemingly carefully 
erected towers. More knowledge concerning the winter habits 
of the animal, and its mode of life during the breeding season, 
would perhaps throw light upon the purpose of the towers and 
burrows. 

C. diogenes is not plentiful in Central Missouri, and in this 
region the mud chimneys are built about eight inches high, and 
are formed of pellets of mud of regular size and shape. On the 
inside the chimneys are plastered smooth, and outside they have 
the characteristic rough appearance due to being formed of 
mud balls. 


GROUP TV. 


The remaining species of crayfish found in Missouri belong 
to Group IV. 

A male of this group is easily distinguished from one of 
any other group by the form of the first pair of abdominal 
appendages, which are more slender than in any other, and in 
the first-form males they are always terminated by two slender 


(23) 


and, in most species, nearly straight styliform tips. 

Beginning with the species which is least plentiful in this 
state, I shall treat of the members of this group in the order of 
their abundance. 


CAMBARUS HARRISONII, Faxon. 


This species has been reported from but one locality in the 
state, Irondale. We have no specimens in the collection here. 
Faxon (loc. cit. p. 95) says that C. harrisonit resembles 
C. rusticus in general form, but that the first pair of abdominal 
appendages of the male and the annulus ventralis of the female 
differ conspicuously from any other species of the group. 
Faxon figures the first pair of abdominal appendages very short 
and thick; the rami short, rather blunt and slightly curved. 
These appendages would suggest a close relationship with 
Group III. C. harrisonu is probably a border species. No 
second-form males have been reported. 


CAMBARUS WHITMANI, N. SP. 
Plate Vi, (Rie. (By (Plate 10.) Pigs. (\Crand@2) 


This crayfish was taken from the James River, Missouri, 
on August 20, 1897. It appeared at first to be a variation of 
C. palmeri (Faxon), but upon careful examination I find that it 
differs in important distinguishing characteristics. No other 
species has been described with which this species can be 
identified. 

Male, form IJ. —- Rostrum long, deeply excavated, margins 
nearly parallel from base to lateral spines, which are acute, 
short and corneous; acumen long. Postorbital ridge termi- 
nated by a blunt spine. Carapace punctate above and granulate 
on the sides; lateral spine large; portion behind cervical groove 
flattened ontop. Areola very narrow, with a small anterior and 
large posterior triangular field. The length of the areola is 
one-half the distance from the cervical groove to the tip of the 
rostrum. Abdomen broad, as long as the cephalothorax. 
Proximal segment of the telson bispinous on each side, distal 
segment slightly concave on posterior border. Antennz long; 
lamine slightly longer than the rostrum, broadest in the middle, 
tapering to a short spine at the apex. Third maxillipeds hairy 
within. Anterior process of the epistoma notched at the apex. 
Chelz long, smooth and punctate, margined on the outer edge. 
Hand straight, inner margin straight and short, with a double 


(24) 


row of small ciliated tubercles. Fingers long and straight, 
with corneous incurved tips, punctate and ciliate above. Mov- 
able finger furnished with a double row of ciliated tubercles 
on basal half of the outer edge. Outer finger hairy below at 
the base. Opposable edges of the fingers bluntly tuberculate. 
Carpus with three spines on interior border; smooth below, 
with two prominent anterior spines. Meros with two spines 
on upper surface, outer row of inferior biserial spines reduced 
to two well-developed spines, large sharp spine on anterior 
border. Third pair of legs hooked. First pair of abdominal 
appendages articulated at the base, stout, long and straight, 
bifid for a short distance from the tip, rami divergent, outer one 
the longer. 

Below are given the measurements of a large male, form 
II.: Length from tip of rostrum to tip of telson, 120 mm.; 
length of rostrum, 14 mm.; breadth of rostrum at the base, 
5.5 mm.; length from tip of rostrum to cervical groove, 40 mm. ; 
length of areola, 20 mm.; breadth, I mm.; outer margin of 
hand 68.5 mm., inner margin 15 mm.; movable finger, 49 mm. 

This species is closely related to the recently described sub- 
species C. palmeri longimanus (Faxon); in some particulars it 
resentbles it more than C. palmert. But the shape of the hand 
and the first pair of abdominal appendages is so different that 
they can not belong to individuals of the same species. 

Plate III., Figs C1 and C2 show the hand and first pair of 
abdominal appendages of the male of C. whitmani, whose meas- 
urements are given above. The hand is drawn natural size and 
the appendages one-half longer than natural size. 

Plate VI., Fig. 2 is reproduced from a photograph of the 
same individual from which the hand and abdominal appendages 
are drawn. 


CamBarus IMMUNIS, HAGEN. 
lated Bigs. On to 102) Bt toh 3. 
For synonomy see Faxon (’89, p. 99). 


Until recently this species had been reported from only one 
locality in the state, St. Louis. During the period covered by 
my studies it has been collected from a number of localities in 
the northern part of the state. We have in the collection here 
specimens from St. Louis; Mexico, Audrain County; Canton, 
Lewis County; Chillicothe, Livingston County; Martinston, 
Putnam County, and from St. Joseph. 


(25 


This species inhabits ponds and creeks, and in rainy weather 
individuals are often found crawling freely about in the meadows 
and fields and along the roads. 

In typical specimens C. tmmums has a rostrum without 
latent teeth, but it is not unusual to find, especially in young 
individuals, smal! rostral spines. 

Our collection of C. 1munums contains seventy-five or eighty 
specimens, too small a number to base a study of variation 
upon. However, the following differences have been noted: 

Plate III., Fig. D1 shows the chele, first pair of abdominal 
appendages and the rostrum of a first-form male 67 mm. in 
length. Hand with curved external border, movable finger 
with characteristic notch on the inner border; base of fingers 
densely setose. Two spines on internal border of carpus, one 
spine on upper surface of meros. Rostrum triangular and 
sharp-pointed. Abdominal appendages small, curved and with 
scattering sete on the proximal half of the internal border. 

Plate III., Fig. D2 shows chelz, rostrum and first pair of 
abdominal appendages of a first-form male 73.5 mm. in length. 
This specimen is from the same locality as the specimen of 
Fig. Dt. The hand is long, narrow and straight and without 
the notch at the base of the movable finger. The carpus has 
two spines on the inner border. Meros is destitute of spines 
on upper surface. The sete are less developed, both on the 
chelz and on the abdominal appendages, than on the specimen 
of Fig. D1. The rostrum is broader and more sharply pointed. 
This claw without a notch is, I think, a regenerated one. I 
infer this from the fact that in several instances I have found 
individuals upon which the claw on one side was without the 
notch, while the one on the other side had the notch. In every 
instance where this is the case the claw without the notch is the 
smaller of the twe. I have also found specimens where both 
chelz were devoid of the notch. On the same hypothesis I 
take it that in such cases both chele have been taken off, and 
that these straight claws are regenerated ones. ‘This view is 
borne out by the fact that such claws are always undersized 
for the individual. I have not observed the regeneration of 
a chele in C. immunis, but in C. virilis the regenerated claw 
passes through at least two moults before it takes on the 
appearance of a normal claw. The notched or hooked appear- 
ance of the claw of C. wmmuntis is mainly due to the presence of 
two or three large tubercles above the base of the inner margin 
of the movable finger. In regenerated claws of C. wirilis the 


(26 ) 


usual spines and tubercles are not always present, and then only 
after two or three moults. This may also be the case in 
C. mmunis. Judging from the size of the unnotched claws 
sometimes found upon individuals of C. immunis, several moults 
have certainly taken place since the original chela was lost. 

Plate III., Fig. D3 shows the chelz, rostrum and first pair 
of abdominal appendages of a first-form male 71 mm. in length. 
The right hand shows the notch, and the left one is without it. 
It is noticeable, also, that the sete are better developed on the 
right hand than on the left. Each carpus shows two spines; 
on the right meros and one inconspicuous spine on the 
left one. Rostrum with concave edges. Abdominal append- 
ages slender and less curved than in typical specimens; sete 
on median border. 

There are some constant differences between the first and 
second-form males. ‘The hand of a second-form male is always 
relatively much smaller than of a first-form male. It is shorter, 
narrower and thinner, and the spines and sete are less devel- 
oped. ‘The following are the measurements of the chelz of two 
specimens each, of first-iorm and second-form males: 

First-form male: Length, 71 mm.; length of outer margin 
of hand, 33 mm., length of inner margin 31 mm., breadth 11 mm. 

secomd-iorm male: Length, 71.5 mm.; length of outer 
margin of hand 25.5 mm., length of inner margin 24 mm., 
breadth 8 mm. 

First-form male: Length, 59 mm.; length of outer margin 
of hand 26 mm., length of inner margin 24.5 mm., breadth 9 mm. 

Second-form male: Length, 61 mm_.; length of outer 
margin of hand 19 mm., length of inner margin 18 mm., breadth 
6.5 mm. 

Plate III., Figs. Er and E2 show the chelz (natural size) 
of the specimens from which the first pair of measurements 
were taken. In general, the rostrum of the first-form male is 
less excavated than that of the second form. In some first-form 
males the rostrum is nearly plane, but it is usually slightly 
excavated. 

The female C. immunis has the abdomen noticeably broader 
than the male, so much broader, in fact, that the sexes can be 
recognized at a glance by this one feature. The hand of the 
female is also relatively much shorter. A comparison of Figs. 
Er and E3 of Plate ITI. will show the relative proportions of the 
hands of the male and female. Fig. Er is a chela of natural size 
from a first-lorm male, 71 mm. in length. Fig. E3 is a chela, 


(27) 


also natural size, from a female 80 mm. in length. The species 
are no better developed on the hand of the female than on the 
hand of the second-form male, but it is thick and short instead 
of thin and narrow. 


CAMBARUS RUSTICUS, GIRARD. 
Plate il Piss. ji tong 


This species is widely distributed over the United States, 
and has been reported from several localities in Missouri. In 
the collection we have specimens from the Osage River, Spring- 
field, Marshalfield, Mt. Vernon, Linn Creek, and perhaps 
Columbia. Several individuals of C. rusticus were found in a 
large collection of alcoholic specimens of C. wirilis taken at 
Columbia, but whether they were captured with the C. wirilts 
or were introduced into the collection is uncertain. ‘The species 
is not common in the locality. 

Faxon (85, pp. III, 112) suggests that under C. rusticus, 
C. placidus (Hagen), C. juvenilis (Hagen), and also C. wiscon- 
siensis (Bundy), should be included. He says of the above 
mentioned species: “After a careful comparison of all the 
species before me, I am inclined to unite them all as forms of 
C. rusticus.” 

As would be inferred from this, C. rusticus is subject to 
considerable variation. Faxon mentions variations in the chele, 
rostrum and first pair of abdominal appendages; also variations 
in the shape of the areola. He gives the type description of the 
hands, as iollows: “ Fingers gaping at the base, not bearded; 
movable finger incurved, external margin convex.” However, 
individuals with external margin of the hand straight are not 
unusual.” Faxon also mentions that in a collection of C. rus- 
ticus from Yellow Springs, Ohio, the young specimens, about 
20 mm. Ieng, have a dense beard on the inner side of the 
external finger, near the base. The rostra of all the individuals 
agree in being excavated, and in having thickened margins; but 
the rostra may be long or short, with or without rostral spines, 
and may sometimes have a median carina near the tip. Faxon 
speaks only of young specimens as having rostral spines. The 
first pair of abdominal appendages are usually. straight and of 
medium length, but in some individuals these appendages are 
found to be considerably curved and longer than the type speci- 
mens. The areola is usually of moderate width, with sides 
parallel for a part of its length; but in some specimens the 


(28 ) 


ateola is narrow at a point in front of the center, and conse- 
quently its sides are not parallel. 

Besides the above mentioned variations described by 
Faxon, the individuals which 1 have examined show other 
departures from the type description. 

C. rusticus is described as having an areola equal in length 
to the distance of the cervical groove from the base of the ros- 
trum; an abdomen a little shorter than the cephalothorax, and 
the anterior process of the epistoma blunt. In the specimens 
before me the areola is uniformly shorter than the distance from 
the cervical groove to the base of the rostrum, and instead of 
the abdomen being shorter than the cephalothorax, the reverse 
is the case; the epistoma, instead of being merely blunt, is often 
slightly notched. 

The variations among individuals of the collection are so 
marked that without a series of specimens ranging from 25 to 
100 mm. in length, the species would be very hard to identify. 
But with a series of specimens collected at the same time and 
place, one can not fail to see that they all belong to the same 
species. 

With only a few individuals to study, one might easily 
classify members of this species as C. medius (Faxon), or C. neg- 
lectus (Faxon). In a number of characteristics C. rusticus and 
C. medius are identical. The features by which C. rusticus is to 
be distinguished from C. medus are differences in the rostra, in 
the length of the first pair of abdominal appendages, the relative 
length of abdomen and cephalothorax, and the areolez.. 

In certain individuals of C. rusticus the rostrum is broad, 
without spines and with a median carina near the tip. The 
carina makes the rostrum answer to the description of the ros- 
trum of C. medius. ‘The chief difference between the abdominal 
appendages of the two species is that in C. medius the rami are 
longer than in C. rusticus. Whenever the rami of C. rusticus 
are a little lengthened, we have the C. medius form of appendage. 
C. rusticus is described as having an abdomen a little shorter 
than the cephalothorax, while C. medius is described as having 
‘an abdomen and cephalothorax of equal length; but in the 
specimens which I have, the abdomen is uniformly longer than 
the cephalothorax, so that this can not be Hee as a character 
by which to distinguish the species. 

[I was at first inclined to identify them all as C. medius. 
However, at the suggestion of Dr. Ayers, under whose direction 
I have done the work, I sent several individuals to Professor 


(29) 


Faxon in order to get his opinion as to what specific name 
should be applied to them. I sent two large ones and three 
small ones. Faxon classified them as two species, a thing which 
I think he would not have done had he had a complete series 
before him. His classification is C. rusticus and C. neglectus. 
Here again the chief features distinguishing these two species 
are shape of rostra and relative length of abdomen and cephalo- 
thorax; the first pair of abdominal appendages and the develop- 
ment of spines on the lower surface of the meros. As already 
noted, the rostrum is quite variable; in the specimens before me 
there are all gradations between the form of rostrum described 
for C. neglectus and that described for C. rusticus. C. neglectus 
is also described as having an abdomen larger than the cephalo- 
thorax. ‘This is true of all the specimens before me, not only of 
the specimens described as C. neglectus, but also those described 
as C. rusticus. The first pair of abdominal appendages of the 
first-form male of C. neglectus are described as nearly straight 
and so long that when turned forward the tips of the rami reach 
the base of the chele. These appendages in C. rusticus are also 
nearly straight, but are only long enough to reach to the base 
of the second pair of legs. A slight decrease in the length of 
the rami of C. neglectus is all that is necessary to reduce them to 
the C. rusticus form. In one of the specimens that Faxon 
classified as C. neglectus these appendages are no longer than 
demanded by the description of C. rusticus. In C. neglectus the 
lower surface of the meros is described as having two rows of 
spines; in C. rusticus all of these inferior biserial spines are 
described as only slightly developed, except the apical one of 
each row. More often than not, these spines in the species 
described as C. neglectus are reduced to low blunted tubercles, 
thus bringing them to the C. rusticus form. There is one more 
point that should be mentioned, viz.: in C. rusticus the antennal 
scale is described as slightly longer than the rostrum, while in 
C. neglectus the antennal scale is described as equal in length to 
the rostrum, but in the individuals described as C. rusticus the 
antennal scale is sometimes no longer than the rostrum; so that 
feature is also useless as a means of classification. 

Since in the eighty-five individuals which I have before me 
not a single character that would separate them into C. rusticus 
and C. neglectus is found to hold throughout, we must conclude 
that they are all variations within one species. If I had only 
the extremes to judge from, I should not hesitate to separate 
them into two species. However, the general contour of the 


(30) 


body and the general form of the first pair of abdominal appen- 
dages of the male remains constant throughout the series. 
This, together with the fact that all of these varying gradations 
are found among individuals that have spent their lives in the 
same stream, and when they were collected were captured at 
the same time, seems to indicate that whatever these variations 
may lead to in the future, they should now all be included under 
one species. 

That these variations form a graded series in which there 
is no definite dividing line, I have attempted to show by means 
of the photographs reproduced in Plate VI. 

These photographs show a series of the differences in form 
of chele, rostra and general body contour typical of the col- 
lection. It is evident that in a series such as this it is not per- 
missible to say that a certain number of these individuals should 
be classed as one species and the rest as another. 

Plate VI., Fig. 1 is one of the specimens which Faxon 
classified as C. neglectus. According to the same classification, 
Figs. 2, 8, 9, 11, 12 and 13 would also be called C. neglectus. 
Figs. 3, 4, 5, 6, 7 and 10 would be classed as C. rusticus.. Figs. 
4,9, 12 and 13 are females; the remaining specimens are males. 

In looking over the figures shown in Plate VI. no one will 
deny that there are some differences which at first sight may 
appear conspicuous, but these differences are not characteristic. 
We look at the crayfish called C. neglectus, and decide that a 
certain form of chela is characteristic; but on the crayfish 
classed as C. rusticus we find the same sort of chela. If any 
other character be selected we find the same difficulty. Nota 
single individual can be found that exactly accords with the 
description of either species. 

Since this is the case, and since C. rusticus is an old species, 
it having been nearly half a century since Girard named it, I 
have, as was mentioned above, classified the whole series under 
C. rusticus. ‘The species C. medius, which I shall take up next, 
seems to me to belong under C. rusticus also. 


CAMBARUS MEDIUS, Faxon. 


C. medius has been reported only from Missouri, and from 
but one locality, Irondale. The only specimens which are 
known to have been collected are the two from which Faxon 
named this species. The likenesses and differences between 
this species and C. rusticus have already been mentioned in dis- 
cussing C. rusticus. As has been shown, the differences which 


(31) 


separate the three species, C. rusticus, C. neglectus, and C. medius, 
are very slight and inconstant. Knowing, as I do, the vari- 
ability of the individuals within the species C. rusticus, and con- 
sidering the fact that Faxon had but two specimens from which 
to name the species C. mediis, it seems to me quite probable 
that those individuals which Faxon calls C. medius are variations 
of C. rusticus; and I think that he would have recognized them 
as such if he had been able to examine a number of individuals. 

I think that a careful comparison of the descriptions of 
these three species, together with an examination of the varia- 
tion within the one species C. rusticus, proves that not a single 
feature which would distinguish one species from another holds 
through a single series of specimens taken at the same time and 
place. If one character —e. g., relative lengths of abdomen and 
cephalothorax — tells in favor of identifying the specimen as 
C. rusticus, some other character —e. g., length of first pair of 
abdominal appendages—answers to the description of C. medius. 
In not a single individual that I have examined have the main 
distinguishing characteristics between these three species been 
united. It is clear that such extremely variable characters have 
not the value of specific characters. 

Within the species of which I have had abundant material 
to examine (C. virilis), there are greater and more numerous 
variations among individuals coming from the same pond than 
are used to separate the three species, C. rusticus, C. neglectus 
and C. medius. 


CAMBARUS VIRILIS, HAGEN. 


Platesol and Ui: 
For synonomy see Faxon (loc. cit. p. 96). 


C. virilis is the most common species in the state. It is 
found in great numbers wherever it occurs, and it is widely dis- 
tributed. It has been collected from the following localities in 
Missouri: St. Louis, Osage River, Irondale; Washington, 
Franklin County; Kansas City; Niangua River, Camden 
County; Marmaduke, Lawrence County; Linn Creek and 
Columbia, Boone County. Most of the above named places are 
situated in the central and southern part of the state. 

C. virilis is especially plentiful in the ponds and streams 
about Columbia. Upon one occasion in June, 1896, Dr. Ayers 
collected in the course of two and a half hours more than five 
hundred crayfish of this species. ‘There is one lot in our present 


(32) 


collection which contains over twelve hundred individuals. The 
whole collection of C. virilis contains over three thousand speci- 
mens. In general the number of females collected exceeds the 
number of males; although in one or two lots in the collection 
the mailes are in excess of the females. In one lot, taken at 
Columbia in 1897, there are 162 males and 203 females. Among 
212 crayfish collected during April, 1899, 80 were males and 132 
were females. In most collections the males and females are 
in about the above proportions. 

The abundance of C. virilis renders it an excellent subject 
for the study of variations within a species, and for a comparison 
of the differences between the first- and second-form males. 

A special discussion of second-form males will be taken up 
later. Here it may be mentioned that, besides the difference 
in the form of the first pair of abdominal appendages, which 
separates the males into first and second forms, there are other 
noticeable differences between the two forms. Especially 
noticeable is the difference in the relative size of the chele. The 
394} JO uostiedwi0d YW ‘dzIs sUIeS 9} JO S[ENPLAIpUL WIoj-jsIg 
chelz of the second-form individuals are much smaller than in 
Bios, K and i, of Plate I. shows this difference. Fig. K is full 
and broad, and with outer margin of hand considerably curved. 
Whe spines and tubercles are well developed. In Fig. L, the 
hand is thinner and narrower, and the outer margin is nearly 
straight. The spines and tubercles are less developed than in 
Fig. K. The crayfish from which Fig. K is taken was 67 mm. 
long, and the one from which Fig. L, is taken was 68 mm. long. 

A still more remarkable difference is seen between Figs. N 
and O of Plate Il. The crayfish from which the former is taken 
was 74 mm. long, and the one from which the latter is taken 
78 mm. long. There was no great difference in the size of the 
two animals, but a very marked disparity existed in the size of 
the two chelz. The figures are life-size in all cases. For 
Fig. N the measurements of the hand are: length, 23 mm.; 
breadth,g mm. For Fig. O: length of hand, 39 mm.; breadth, 
14mm. These two chelz also show a more marked difference 
-in the development of the spines than Figs. K and L. 

Immature C. viriis: Even in very young individuals 
and chele. : 

C. virilis presents a number of variations. The variations here, 
as in older specimens, are to be noticed mainly in the rostra 

As is well known, the newly hatched crayfish is in some 
particulars very different from the adult individual, and it will 


(33) 


be necessary to speak of some of these differences first. 

When the little animal first comes from the egg the cephalo- 
thorax is very large in proportion to the abdomen. The abdo- 
men, thoracic legs and the antenne are flexed under the almost 
spherical cephalothorax. The different parts of the cephalo- 
thorax can not at this time be distinguished. The rostrum is 
very short and bent down between the eyes; the chelz present 
very little of the appearance of the chele of the adult. The 
beginning of the suture which is to form the joint of the movable 
finger is only visible under considerable magnification; the 
tips of the chelz are furnished with recurved hooks; this is 
also true of the other chelate appendages, but their hooks are 
not so strongly recurved as in the chele. 

With a magnification of one hundred diameters small spines 
and setz are visible on various parts of the exoskeleton. 

No appendages are present on the first and sixth abdominal 
somites: however, the appendages of the sixth somite are 
already formed and inclosed beneath the telson, from which 
they are set free after the animal moults. 


The crayfish when first released from the egg is quite help- 
less, and it remains attached to the swimmerets of the mother 
for some time. The muscles are still in an embryonic condition. 


Within five or six days a considerable development has 
taken place, although no moult has intervened. The animal 
is able to swim about; the relative size of the cephalothorax 
is not nearly so great. The remnant of food yolk which was 
stored up in the cephalothorax has diminished considerably, 
and now, instead of forming a continuous mass, has separated 
into twc masses, one on either side of the median line, with a 
clear space between. The cervical groove and areola area can 
now be distinguished. The spines and sete are much better 
developed than when, the crayfish came from the egg. 


In about nine days after hatching the first ecdysis occurs. 
At this time the telson fins are set tree, and the spines and sete 
show a marked increase in size. The rostrum is much length- 
ened, and is no longer bent downward between the eyes; small 
rostral spines have made their appearance. The chele have 
lost their recurved hooks. The abdomen and cephalothorax 
have assumed about the same relative proportions as are found 
in the adult. The appendages of the first abdominal somite 
have net yet appeared, although a minute swelling under the 
skin car be seen, and the appendages will be set free after the 


(34) 


next moult. The animal at this stage measures 7to8 mm. I 
have seen these appendages on C. gracilis 15 mm. long. The 
appendages had evidently just appeared, for previous to this 
they were simple little buds, without any differentiation into 
segments. At 18 mm. there is a separation into protopodite 
and distal portion of the appendage, but no division indicating 
a separation into endopodite and exopodite. Whether these 
appendages appear earlier or later in C. wirilis, I do not know, 
having had no specimens of this species to examine; but I think 
it probable that C. vwirilts would be somewhat larger, since the 
adults in C. virilis are of somewhat greater size than C. gracilis. 

After the first moult the young crayfish do not yet leave the 
protection of the mother, but either attach themselves to or 
detach themselves from the swimmerets of the female, as suits 
the occasion. 

A small part of the food volk still remains, but in four or 
five days after the ecdysis it has all disappeared, and the little 
animal must then shift for itself. 

At this stage the young crayfish are almost transparent, 
and by placing a live one under the microscope the circulation 
of the blood in the gills, the beating of the heart and the passage 
of the water through the gill chambers may be observed. From 
the ventral side can be seen the double nature of the nerve cord 
through the length of the abdomen and a part of the cephalo- 
thorax. 

The areola is relatively broader in the young crayfish than 
in the adult. A crayfish about nine days old, 8 mm. long, has 
an areola .2 mm, wide; that is, the breadth of the areola is to 
the length of the animal as 1 to 27; a crayfish 68 mm. long has 
an areola about 1 mm. wide; thus the relative length of body 
and areola is as I to 68 in the adult. 

The gill system of the newly hatched crayfish appears to 
be identical with that of the adult. I have examined a number 
of crayfish just from the egg, and in no case have I been able 
to discover any trace of a gill on the last thoracic somite. 

I was enabled to make these observations on the very 
young by taking females in berry and hatching the eggs in the 
laboratory; thus tar I have succeeded in studying them from 
the time of hatching through the first moult. 

At this very young stage but little variation can be noted. 
By the time they are 9 or Io mm. long, variations are conspicu- 
ous. One of the most noticeable points of difference at this 
stage is seen in the length and shape of the rostrum. Some of 


(35) 


them show rostral spines by the time they are Io mm. long, 
others show no signs of these spines; but then we often find 
mature C. virilis devoid of rostral spines, and it may be that the 
adult individuals, instead of having lost these spines in the 
course of development, have never possessed them. 

At 9 or 10 mm. the chelz show nothing particularly char- 
acteristic of C. virilis, but variations in the relative proportions 
of the appendages are already present. 

By the time the young animal is 18 mm. long, the chelze 
show a characteristic which is one of the most constant of the 
species, namely, the smooth, thickened margin on the outer 
contour of the hand. ‘This margin is always present in a regen- 
erated claw; after the first moult, and so far as my experience 
with the species goes, it is the only characteristic that may be 
considered absolutely constant. | 

There is some variation in relative lengths of abdomen and 
cephalothorax. The following is a table of measurements 
taken from individuals varying from 35 to 45 mm. in length: 


LENGTH OF LENGTH OF 


LENGTH OF BODY 
ABDOMEN CEPHALOTHORAX 


35.00 mm.| 20.10 mm. 15.00 mm. 
44.00 “* 24.00 20.00 

44.00 ‘* D300. Ni 2100) 
40.00 “S DAC5O) 18.50 ‘ 
35.00 “‘ 18.50 ° 16,50! 7%) 
44.00 “‘ 24.00 “° 20.00 “° 
ARNO ty ns 23.00 “° 20.00 “° 
44.00 “° DO SOUN PASO ie 
ADIOON eh 2200) ry 20.00 ‘‘ 
ADO ai 2? OOK. si: 20.00 “* 


It is to be noticed that these variations are not so marked 
as those found in C. gracilis, although in other respects 
C. gracilis is by far the more constant species. In C. wirilis the 
abdomen is in every case longer than the cephalothorax. 

Much greater variation is found among adults of C. virilis 
than among the young; even though they have been collected 
in the same vicinity, out of the same pond or creek. 

Following are the descriptions of a number of figures which 
show the variations in rostra, chelz and first pair of abdominal 
appendages of the male. urd 


(36 ) 


Plate I., Fig. A shows the chelz, rostrum and first pair of 
abdominal appendages of a first-form male 106 mm. in length, 
taken at Columbia. The hand is long, thin and very spinous, 
and with outer contour very much curved. ‘The carpus has two 
well-defined spines on the median border. The meros two 
spines on its upper border. The rostrum is long and narrow, 
with the rostral spines almost obsolete. The abdominal 
_ appendages have three well defined tufts of sete arranged along 
their inner borders. ‘The tufts of sete on the lower projection 
is very unusual. 

Plate I., Fig. B shows chela, rostrum and first pair of 
abdominal appendages of a first-form male 80 mm. long. This 
individual was also taken at Columbia. The general outline of 
the hand is much the same as in Fig. A, but the spines are not 
so well developed and the hand is not so thin. There are three 
instead of two spines on the upper border of the meros. The 
rostrum is especially noticeable on account of its many angles. 
This form of rostrum is not common. The abdominal append- 
ages have only two tufts of sete, and are not so much curved 
as in Fig. A. 


Plave l) Hig. C shows chela, rostrum and first pair of 
abdominal appendages of a first-form male 71 mm. long, col- 
lected at Columbia, 1895. This shows a hand relatively much 
shorter and thicker than the previous specimens. ‘The spines 
-are much less developed than in Figs. A and B; the distribution 
is about the same, except that on the meros there is but one 
spine, and that one small. The rostrum is short and broad, 
with an obtuse apex and no spines. The abdominal appendages 
are thicker compared with their length than in the preceding 
specimens. 

Plate I., Fig. D shows chela, rostrum and first pair of 
abdominal appendages of a first-form male 82 mm. in length, 
taker: at Columbia, 1895. The hand is long and thin, the spines 
smal! and the movable finger crooked. The carpus has three 
spines on its inner border, and the meros has but one on its 
upper border. The rostrum is of medium length, the sides 
-almost parallel and the acumen acutely angular. The abdomi- 
nal appendages are relatively long and slender, and show but 
one well developed tuft of sete. 

Plate I., Fig. E. shows chela, rostrum and first pair of 
abdominal appendages of first-form male 91 mm. in length. 
The hand is long and thin, the opposable edges of the fingers 


(37) 


bordered by large, blunted spines. On the median border of 
the carpus is a very large spine and one small one; on the 
uppet surface is a group of three small spines. ‘The meros has 
two spines on its upper surface. The rostrum is long and 
narrow, with convex apex, and entirely destitute of rostral 
spines. The abdominal appendages are long, slender, and less 
curved than in some individuals; they show two tufts of sete, 
one on the lower median projection, which is not at all common 
in any species with which I am familiar. 

Plate I., Fig. F shows rostrum and first pair of abdominal 
appendages of a second-form male 102 mm. long, taken at 
Columbia in the same collection as Figs. C, D and E. No 
normal chelz were present, which is the usual state of affairs 
in a large second-form male. The rostrum is long, with sides 
slightly concave, and with the base very little broader than the 
distal end; sides of the apex also concave, acumen sharp- 
pointed, with small median carina. The abdominal appendages 
are long, slender and considerably curved. 

Plate I., Fig. G shows rostrum and first pair of abdominal 
appendages of a second-form male 98 mm. long. This is also 
from the same collection as Fig. F, being short, almost tri- 
angular, with a very broad base, and with an extremely acute 
acumen, and with conspicuous rostral spines. The abdominal 
appendages are not so strongly curved or so slender as in 
Bioe 

Plate I., Fig. H shows chela, rostrum and first pair of 
abdominal appendages of a first-iorm male 98 mm. in length, 
belonging to the same collection as the preceding figures. The 
hand has a strongly curved external margin, and the inner 
margin of the fingers are widely gaping and bordered by well 
developed, blunted spines. The carpus is furnished with two 
sharp spines on its median border. The meros has but one 
spine on its upper surface. The rostrum is triangular, of 
medium length, and has a very sharp apex. The abdominal 
appendages are long, much curved, and show two tufts of setz 
on median borders. 

With the exception of the first two above described figures 
(Figs. A and B), all of the individuals from which these figures 
were drawn were collected in the same vicinity during the same 
year. The specimens from which Figs. A and B were drawn 
were collected in the same vicinity, but not during the same 
year. These crayfish had passed their lives under practically 
identical conditions, and vet present marked variations. Still 


(38) 


each individual presents enough of the characteristics of the 
species to make it certain that they all belong to the same 
species, wide apart as the extremes are, for there is a closely 
graded series of intermediate stages. Crayfish from different 
localities within the same state also show variations, but not 
more marked than those which are to be seen among individuals 
of the same locality. 

I have had no opportunity to examine an extensive series 
of the same species coming from different states; but it seems 
reasonable to suppose that these might show variations different 
from those among individuals of practically the same locality. 

Following is a further description of the variations of 
C. virilis, all of which were taken in Missouri. 

Plate I., Fig. I shows chela, rostrum and first pair of 
abdominal appendages of a second-form male 74 mm. long, 
taken November, 1898, at Columbia. The hand is small and 
the spines adorning it are small; both are relatively much 
smaller than the hand and spines of a first-form male of the 
same size. The rostrum is long, with parallel sides, a very 
sharp acumen and no lateral spines. The abdominal appendages 
are slender and straight, with curved tips. 

Patewe, Fier} shows chela,, rostrum: and) first pair of 
abdominal appendages of a first-form male 62 mm. in length, 
taken at Columbia, November, 1898. Hand is relatively much 
thicker than that of the second-form male shown in the pre- 
Geqine fietire; the spines are also much better developed. 
Movable finger is considerably curved; carpus with one very 
prominent spine and two smaller ones; meros with two sharp 
spines on upper surface. Rostrum triangular, with sharp- 
pointed acumen. Abdominal appendages with a gradual curve 
throughout their whole length. 

Plate I., Fig. K shows chela, rostrum and first pair of 
abdominal appendages of first-form male 67 mm. long, taken 
at Columbia. External border of the hand strongly curved, 
spines small. Carpus with two well developed spines on median 
border; a row of small tubercles on the upper surface. Two 
smali spines on the upper surface of meros. Abdominal append- 
ages more slender and less curved than in Fig. J. 

Plate II., Fig. L shows chela, rostrum and first pair of 
abdominal appendages of second-form male 68 mm. in length, 
taken at Columbia. Hand small and their spines small. Carpus 
with one large and two small spines on internal border. Meros 
with two inconspicuous spines on its upper surface. Rostrum 


(39) 


long, with parallel sides and very sharp acumen. Abdominal 
appendages slender and straight, except at the tips. 

Plate II., Fig. M shows chela, rostrum and first pair of 
abdominal appendages of a first-form male 111 mm. in length, 
taken at Columbia, March, 1897. This figure should be com- 
pared with Plate I., Fig. A, for both crayfish were taken from 
the same pond at the same time. The hand is very large and 
thick, with a much curved external border; opposable edges 
of the fingers bordered with large, blunted tubercles. Carpus 
with one long and two short spines on median border, and with 
small tubercles scattered about on the upper surface. Meros 
with well developed spines on the upper surface. Rostrum 
large, with parallel sides, median carina in distal third, rostral 
spines almost obsolete, acumen sharp and long. Abdominal 
appendages long and slender, with three tufts of seta. As was 
mentioned in connection with Fig. A of Plate I., the tufts of 
sete on the lower median projection is quite unusual in this 
species. 

Plate II., Fig. N shows chela, rostrum and first pair of 
abdominal appendages of a second-form male 74 mm. in length, 
taken in Camden County, March, 1897. Hand very small and 
straight, with very small spines. Carpus with well developed 
spine on the median border. Meros with two small spines. 
Rostrum short, broad, triangular, with obtuse acumen. Abdom- 
inal appendages straight and slender, setz very inconspicuous. 

Plate II., Fig. O shows chela, rostrum and first pair of 
abdominal appendages of a first-form male 78 mm. in length. 
Hand large and thick, with external border much curved, 
tubercles and spines well developed. Carpus with two well 
developed spines on median border. Meros with two small 
spines on upper surface. This chela shows a marked difference 
from the one shown in Fig. N of Plate II.; although there is 
very little difference in the size of the crayfish from which the 
two were taken; and it should be added that the two individuals 
were found at the same time and place. The rostra in Figs. N 
and O are very similar. The abdominal appendages are much 
alike, except that those shown in Fig. O are much more curved 
than those shown in Fig. N. 

Plate II., Fig. P shows chela, rostrum and first pair of 
abdominal appendages of a first-form male 110 mm. long, taken 
at Mt. Vernon, Lawrence County, April, 1897. Hand very long 
and thin, with small spines, outer margin straight and upper 
surface flat. Carpus with two well developed spines on median 


(40) 


horder. Meros with two small spines on upper surface. It is 
probable that this chela is a regenerated one, for I have seen 
this same form of chela on one side of the body, while on the 
other side the chela was large and thick, but on the specimen 
from which this figure is taken both chelze were of the same 
character and of about equal size. There were also several 
other individuals of the same collection which had chelz like 
these. The difference is so very marked that one would, unless 
he had thick-clawed individuals at hand, be tempted to classify 
the thin-clawed ones as something other than C. virilis. Ros- 
trum broad, with almost parallel sides, and with obtuse acumen. 
Abdominal appendages long and slender, without conspicuous 
sete. 

Plate II., Fig. Q shows chela, rostrum and first pair of 
abdominal appendages of a first-form male 110 mm. long, taken 
at the same time and place as that of Fig. P, Plate II. Hand 
very large and thick, with much curved external border, spines 
well developed, opposable surfaces of the fingers bordered by 
large, blunt tubercles. This hand is markedly different from 
the hand in Fig. P. Carpus with two sharp spines on internal 
besaer-. Rostrum shorter and narrower than in Fig. P. 
Abdominal appendages shorter and not so slender as in the 
preceding figure. 

Plate II., Fig. R shows chela, rostrum and first pair of 
abdominal appendages of first-form male 82.5 mm. long, taken 
at Columbia. Hand short and relatively very thick, movable 
finger crooked. Carpus with one short spine and one very 
small one on median border. Meros with three spines on 
upper surface. Rostrum with concave edge and sharp acumen. 
Abdominal appendages relatively thick, slightly curved, and 
with two tufts of sete. 

It will be noticed that all the above described variations 
have been found among individuals within this state and in 
only three different localities. Individuals from other localities 
might also have been chosen, but from these three I was enabled 
to select all the representative variations that are shown in the 
-collection. 


FIRST AND SECOND FORMS. 


Since the publication of Hagen’s “ Monograph of the North 
American Astacide,” we have known of the existence within 
each species of Cambarus of two distinct forms or varieties of 
the males. This variation finds expression in the shape of the 


(41) 


first pair of abdominal appendages. In consequence of this the 
males are usually designated as firsi- and second-iorm males. 

The first pair of abdominal appendages in the second form 
are similar to the same pair of appendages in the young, imma- 
ture males. In the first-form males these appendages have the 
distal terminations much more slender, and often fine pointed 
instead of blunt,as is always the case with the distal terminations 
in the second form. 

The fact that the second-form appendages have the same 
general form as the appendages of the immature males led to 
the supposition that the second-form males are sterile. Faxon 
states that the testes are smaller and the vasa deferentia shorter 
in the second form than in the first. He also suggests that 
these two forms are alternating conditions in the life of the same 
individual, the first form being acquired during the breeding 
season and the second form during the other seasons. These 
changes, of course, can not take place without intervening 
moults, but Faxon really observed that some crayfish which 
he had in a tank moulted from first-form into second-form. 
However, he did not carry his observations far enough to 
determine when, if ever, they again reverted to the first form. 
Neither has he offered any explanation as to a probable cause 
of the change from one form to the other. 

The fact that a first-form male will moult into a second- 
form precludes the idea that the second form in any true sense 
represents a developmental stage in the individual. Also the 
fact that we often find in C. wrilis and C. rusticus at least small 
first-form males 40-45 mm. long, living side by side with second- 
form males 80-100 mm. long, shows that the size of the indi- 
vidual bears no relation to the condition of first or second form. 
Hence an explanation must be sought elsewhere. 

During the past two years, in the course of my taxonomic 
studies, I have had occasion to examine a great many males of 
each form, especially of the species C. wirilis, This abundance 
of material has given me an opportunity to make very complete 
observations on the two forms. 

In looking over alcoholic specimens, I noticed that when- 
ever I found a large second-form male, 80-95 mm. long, that 
it never had perfect, well developed chele. There were either 
no chelz, or the chelze present were in a very imperfect state 
as regards size and sculpture, indicating that they had been lost 
and were now being regenerated. Finding this uniformly the 
case, I was led to surmise that the existence of first and second 


(42) 


forms is connected with the presence or absence of chele. It 
will be remembered that the chelz of the second-form males 
are always described as smaller and with smaller spines and 
tubercles than those of first-form males of a corresponding size. 

On April 22, 1899, I took a number of large first-form 
males and broke off both chele, expecting them soon to moult 
into second-form individuals. In this I was not disappointed, 
for during the next two or three weeks several of them moulted, 
each one into a second form. However, I noticed a difference 
between the second-form with chelz and the second-form with- 
out chele. The first pair of abdominal appendages of those 
with chelz are not so slender; they are as individuals without 
chelz. The basal half of the appendage has the usual shape of 
the first-form appendages, and although the rami are blunt, as 
is usual with the second-form, they are not so closely approxt- 
mated, and the tip of the inner ramus is more dilated than in 
the second form without chelz. (Plate IV., Figs. A and C.) 
The appendages shown in Fig. A are from a second-form male 
without chelz, and the appendages shown in Fig. C are from 
a second-form male with chele. 

When it was found that the crayfish, whether with or with- 
out chelz, and whether first- or second-form, all moulted into 
second-form, it became evident if there were to be first-form 
males the next year, there must be a second moulting season 
during the summer. For in every case that I have been able 
to observe, a male that is already second-form in the spring, 
moults again into second-form. But, as I stated above, these 
are individuals that have no chele at all, or only imperfect ones. 

That there are really two moulting seasons I had already 
suspected; for while engaged in doing some experimental work 
upon crayfish, I found that usually the animal moulted in April 
or May, and again between the first of June and the last of 
August. However, I was not sure that mutilation did not 
increase the frequency of the moults. But my observations 
between May first and the middle of July, 1899, proved that nor- 
mally each male crayfish moults at least twice a year. The time 
from March to November will include both moulting seasons 
for C. virilis. 

The first moulting season begins in April, and by the middle 
of May very few crayfish can be found that have not recently 
moulted. During the first moulting season all the males moult 
into second-form. However, all the males with large chelz 
have the bases of the first pair of abdominal appendages meet- 


(43) 


ing in the median line, while those males with small chelz, or 
with no chelz, do not have these appendages meeting in the 
median line. (Plate IV., Figs. B and F.) The difference in 
shape and development of the bases, and in the general sculp- 
ture of the appendages, is noticeable in Figs. B and F. In 
Fig. F the appendage has much more of the general appearance 
of a first-form appendage than in Fig. B. 

The fact that all males moult into second-form during the 
first moulting season accounts for the great number of second- 
form individuals that are taken at some seasons, while compara- 
tively few are taken at other times. Males from collections 
made in May are likely to be mostly second-form. But collec- 
tions made after the first of July will contain a relatively small 
number of second-form males. We have one collection made 
in early June that contains over seven hundred and fifty second- 
form males and only five first-form. In the collections made 
in the spring of 1899, before May first, not more than six or 
seven second-form males were taken, and they were all of 
medium size. From the tenth of May to the tenth of June the 
collections contained very few first-form males. 

By the tenth of June the second moulting season is well 
begun, and by the first of July comparatively few second-form 
males are to be found. Although now and then on through 
July and August a moulting specimen may be found. 

‘Having found that all the males, whether large or small, 
moulted into the second form during the first moulting season 
of the spring, I expected to find that at the second moult the 
males with cheiz would again be transformed into first form, 
while those without chelz would retain the second-form append- 
ages after the second moult. That such is really what happens, 
my observations have verified; in every instance males pos- 
sessed of two or even one well developed chela, have at the 
second moulting returned to the first form, and those without 
chela have retained the second-form appendages after the 
second moult. 

This appears to be conclusive evidence that the relation 
between the chelz and first pair of abdominal appendages is 
such a close one that the loss of chelze will produce a change 
in the form of the sexual appendages which is more or less 
permanent. In other words, a first-form male that loses its 
-chelz before or at the time of the first moult, will at the second 
moult still retain the second-form appendages; a crayfish that 
loses its chelz after the first moulting season of any given year, 


(44) 


but before the second moulting season, may or may not moult 
into the second-form again at the second moult, depending upon 
how near the second moult is at hand when the chele are broken 
off. A male having once lost its chelz will continue to moult 
as second-form until the new chelz have attained a considerable 
size. 

In a collection of crayfish brought into the laboratory this 
spring, May to, 1900, I found one about 77 mm. long that had 
recently moulted into second-form, and with both chelz missing. 
The stumps of the chele were quite smooth, and no signs of 
the regeneration of these appendages had yet appeared. Quite 
likely the chelz had been lost during the last moult, which had 
evidently taken place only a few days before. May 13th, three 
days after I had found this crayfish, it again moulted into 
second form. At this moult there was only the rudiment of 
a new chela. A minute bud had appeared, which showed no 
semblance whatever to an appendage. Then on June 17th this 
crayfish moulted for the third time, still retaining the second- 
form appendages. Between the last two moults, May 13th to 
June 17th, the chelz had grown to such an extent that when they 
were released from the confining skin at the third moult, they 
expanded to more than an inch in length. 

August roth this crayfish died without having moulted 
again. At the time it died the chelz measured 36 mm. in length 
and 5 mm. in width, this entire growth having been made in 
three months. 

Judging from the small, imperfectly developed chelze which 
I have seen on the other second-form individuals, I think it 
scarcely probable that, had this crayfish lived through another 
moult, it would have then reverted to first-form, for the chelz 
would still not have been so large as it appears requisite for 
them to be in order that the crayfish be first-form. For it is 
well known that the growth of the chelz is quite slow after the 
moult in which the chelz first appear in the form of true jointed 
appendages. Plate IV., Fig. K, shows the chele, natural size, 
of the crayfish described above. Although this growth took 
place within three months, most of it occurred between 
May 13th and June 17th, very little over a month. The chelze 
were only 36 mm. long when the crayfish died, August toth; 
they were fully 33 mm. long June 17th. Only a minute bud had 
appeared between May 13th and June 17th, and only 3 mm. 
between June 17th and August Ioth, an interval almost twice as 
long. 


(45) 


From the above consideration it is readily seen, on the 
hypothesis that absence of chele is the cause of a crayfish 
remaining second-form through two or more successive moults, 
that it is altogether possible that a crayfish remains second-form 
through several moults —e. g., four or five at least. We have 
positive evidence that they can and do remain second-form 
through three successive moults when the chelz have been 
broken off, and that when chelz are present, the crayfish alter- 
nate from first-form to second-form with each moult. 

I might here add that C. gracilis furnished some negative 
proot that loss of chele perpetuates second-form males. Faxon 
states that second-form individuals among C. gracilis are 
unknown. There are two facts to be noticed which help to 
explain this absence of the second-form in this species. First, 
as I have mentioned in discussing the species, their moulting 
season has never been discovered, and there are, at most, only 
a limited number of males in any collection. Of course, the 
fact that the time of moulting is unknown does not explain 
why the second-form has not accidentally been found instead 
of always first-form. But the extreme scarcity of the males 
may help to explain this. 

The second fact to be noticed in this connection is that 
C. gracilis never shows that there has been a loss of parts, as 
chela or other appendages. When individual C. gracilis are 
first captured, no appendages are broken except those which 
show evidences of having been broken in capturing them. Now 
the only grounds upon which I attempt to explain this are, that 
the external conditions to which the animals are subjected are 
such as favor a minimum of accidents. Living in their burrows 
as they do, it seems that they are able to avoid many misfor- 
tunes which come upon other species of crayfish that habitually 
live in the streams and ponds. In none of the collections of 
C. gracilis which I have seen has there been an individual with 
a broken chela, unless there was evidence that it had been 
recently broken. Since none have moulted in my laboratory, 
of course there is no way of determining whether they moult 
into second-form or not, or whether breaking off the chele 
would cause them to moult into second-form. From what we 
known of other species of Cambarus, it is fair to suppose that 
males of C. gracilis normally have two moulting seasons; at the 
first, sie Hae into pce and: form, and at the second returning 
to first form. 

Experiments have proven that young aC: gracilis repair an 


( 46) 


injury and regenerate a lost or broken appendage as readily as 
the young of any other species. And though they are seldom 
injured, they seem not to have lost in the least the power of 
regenerating lost parts. My observations and experiments on 
this species have been confined to young specimens, 35 or 
40 mm. in length. 

It is not unusual to find first-form males without chele, but 
either only bare stumps are present, or the new growth that 
has occurred shows that no moult has taken place since the 
chelz were broken off. It is quite probable that the chelz were 
broken off during the last moult; for it often happens that a 
crayfish loses one or more appendages in his efforts to free 
himself from his old shell. 

The loss of but one chela does not seem to sufficiently 
derange the mechanism of the animal to change it from first to 
second form. However, in a number of instances I have found 
indications that the loss of one chela affects the reproductive 
organs. 

During March and ‘early April, in making some dissections, 
I noticed in two instances where one chela was missing; that 
on the opposite side of the animal the vas deferens was much 
shorter than on the side from which the chela was gone. 
Having noticed this difference in two instances, I dissected a 
number of other crayfish with but one chela, and in every case 
where it was evident that the chela had been lost for some time 
I found this same difference between the reproductive organs 
of the two sides. ‘The shortening of the vas deferens was always 
on the opposite side from the missing chela, irrespective as to 
‘ whether it was the right or left chela. 

For comparison I examined a number of other males 
having both chelz present. Without exception I found the vasa 
deferentia equally developed on each side. Had I found this 
difference between the vasa deferentia of males with two chele 
and males with one chela to remain constant for all seasons of 
the year, I should have considered it positive proof that the loss 
of the chelz is directly connected with the degeneration of the 
reproductive organs. Although I found this to be true for 
every case examined during the latter part of March and early 
April, in June, when I came to examine males with but one 
chela, this difference was no longer apparent. I can offer no 
explanations for these facts as yet. 

It is well known that the reproductive organs vary consid- 
erably in size and development at different seasons of the year, 


(47) 


being larger and better developed during late summer and early 
autumn, just before and at the time of the breeding season than 
at other times of the year. There is also known to be a differ- 
ence in the relative development of the testes and vasa deferentia 
of the first- and second-form males, but this difference is much 
more conspicuous during some seasons of the year than others. 

During the last few days of March, 1899, and the first two 
weeks of April, I examined the reproductive organs of both first- 
and second-form males. This was done before the first moult- 
ing season began. For comparison I took them in pairs, a 
first-form and a second-form of the same size. In each instance 
I found a marked difference between the reproductive organs of 
the two, especially of the vasa deferentia. In the first-form the 
vasa deferentia were always much convoluted, while in the 
second-form these organs were usually straight, having at most 
not more than one or two convolutions. 

About the first of May I again examined a number of cray- 
fish that had passed through the first moulting season. Then, 
as before, I found that males having the first pair of abdominal 
appendages thick, with rami gaping and tip of inner ramus 
dilated, indicating that the animal was of the form that would 
moult into the first-form at next moult, invariably had much 
convoluted and well developed vasa deferentia. Males whose 
first pair of abdominal appendages were slender, indicating that 
they were of true second-form, had in every case unconvoluted 
vasa deferentia. 

In early June, after the beginning of the second moulting 
season, I again examined first-form and second-form males. 
Althcugh I found that the shape and size of the testes and the 
convolutions of the vasa deferentia of different individuals varied 
considerably, I did not find, as I had previously, that the repro- 
ductive organs of the second-form males were much less devel- 
oped than those of the first-form males. (Plate IV., Figs. D 
and B.) Neither was there any constant difference in the shape 
of the testes of the first-form and second-form males. 

If it is true, as my first observations seem to indicate, that 
a loss of the chelz results in a reduction in size of the repro- 
ductive organs, then a male that loses its chele at second 
moult —that is, when it moults from second-form into first- 
form — should after a time show a degeneration of the repro- 
ductive organs. Proceeding on this hypothesis, I took, June 
27th, a first-form male 90 mm. long, that-had lost its chela in 
the last moult, nearly three weeks before, and for comparison 


(48) 


a first-form male of the same size, with the chelz present, and 
found that the vasa deferentia of the one with chelz were no 
better developed than those of the one without chele. How- 
ever, the testes were larger and better developed. A micro- 
scopic examination showed that the testes of the one with chelz 
were filled with spermatazoa in an advanced stage of develop- 
ment, while the testes of the one without chelz contained very 
few spermatazoa, and these few were in the early stages. 

The reproductive organs from another pair somewhat 
larger, otherwise similar, individuals were then examined. So 
far as size was concerned, there was very little difference in the 
reproductive organs of the two individuals; but microscopic 
examination again showed great numbers of spermatazoa in 
advanced stages in the vasa deferentia and testes of the one 
with chela, and practically no spermatozoa at all in the vasa 
deferentia and testes of the one without chele. 

I then examined the reproductive organs of a first-form 
male 98 mm. long, that had had the chelz taken off April 22d, 
about two months before, and had been in the laboratory since 
that time without moulting. Apparently the testes were much 
degenerated; they were small and semi-transparent. (Plate 
IV., Fig. J.) But the vasa deferentia were large and convo- 
luted; at the ends near the external openings they were opaque 
and milky looking. A part of the distal end of a vas deferens 
Was examined, and found to be filled with spermatozoa of 
advanced stages. 

Whether or not the testes were permanently degenerated 
could not be decided. Certain it was that at that time they 
presented an unnatural appearance. The fact that the vasa 
deferentia were full of spermatozoa does not argue for the active, 
healthy condition of the testes, for it is well known that in many 
animals the spermatozoa retain their vitality for long periods, 
and these spermatozoa which filled the vasa deferentia of this 
crayfish may have been in the vasa deferentia for a long time. 

Although I consider it a well-established fact that pres- 
ence or absence of chelz determines. whether an individual male 
crayfish is to be first or second form, yet at the present there 
appears no way of determining whether the second form is 
sterile or not. 


SUMMARY. 


1. The examination of thousands of specimens of the spe- 
cies C. virilis has led to the conclusion that there are greater 


(49) 


variations within this one species than are often used to separate 
individuals into different species, and the variations involve the 
characters used for classification. 

2. In view of the extremely diverse variations found within 
the species C. rusticus (Girard), it is desirable to include the 
recently described species C. neglectus (Faxon) under C. rusticus, 
since the variations found within this last named species include 
every characteristic that could be used to separate the two 
species. 

3. Relative lengths of cephalothorax and abdomen, length 
of first abdominal appendages of the male, presence or absence 
of spines, shape of chelz and rostrum, can not be relied upon as 
specific distinguishing characteristics; e. g., C. wvirilis shows 
almost every shape of rostrum described within the genus 
Cambarus. 

4. Two new species, C. ayersii, Group I., and C. whitmani, 
Group IV., are described for the first time. 

My work upon the second-form males has led me to the 
following conclusions : 

1. Normaily, in C. virilis at least, every adult male moults 
in the spring into second-form. 

2. Inthe course of six weeks or two months all adult males 
in possession of normal chelz moult a second time, and revert 
again to first-form. 

3. Males without chele or with only imperfect ones also 
moult a second time during the same season, but still retain 
the second-form appendages. 

4. Males without chele or with imperfect ones continue 
to moult into second-form until the chelze have reached a size 
normal for the size of the animal. 

5. In late fall and during winter and spring there is a 
noticeable difference between the reproductive organs of the 
first-form and second-form males, the testes and vasa deferentia 
of the second-form males apparently being much less developed 
than the same organs in the first-form males. 

‘6. During the summer, though the reproductive organs 
of different individuals show great variation, there are no dis- 
tinguishing characteristics by which the reproductive organs 
of first-form and second-form males can with certainty be 
distinguished. | 

7. Though there is some evidence in favor of regarding 
second-form males as sterile, there is as yet no positive proof 
of it. 


(50) 


BIBLIOGRAPHY. 


84. Abbot, C. C—Are the Chimneys of Burrowing Crayfish 
Wesianed: “American Naturalist, Vol. XVII.’ Nov.) p. 
1157. 

85. Abbot, C. C— How the Burrowing Crayfish Works. The 
Inland Monthly, Vol. I., Feb., pp. 31, 32. 

44. Audubon.— Birds of America, 8vo. ed., Vol. VI., p. 57. 

72. Chrantran, S.— Sur la fecundation des ecrevisses. Compt. 
end.) 1:74. pp.)201, 202. Paris. 

85. Faxon.—- Revision of the Astacide. Part I. Genera of 
Cambarus and Astacus. 

89. Faxon.—- Notes on North American Crayfishes, Fam. Asta- 
cidz. Proceedings of the United States Natural Museum, 
Vol. XIL., pp. 625-628. 

"89. Garman.— Cave Animals from Southwestern Missouri. 
Bulletin of the Museum of Comparative Zoology, at Har- 
vard College, Vol. XVILI., No. 6. 

95. Herrick.— The American Lobster. Bulletin of U.S. Fish 
Commission, p. 35, ff. | 

84. Tarr, R. S— Habits of Burrowing Crayfish in the United 
States. Nature, Vol. XXX., June sth, p, 127. 


EXPLANATION OF PLATES. 
Plates I. and II. 


The figures in Plates I. and II. each show chela, rostrum 
and first pair of abdominal appendages (male) of individuals of 
the species C. virilis. In each figure the parts from one indi- 
vidual are grouped together in the same order. 

Fig. A— Ac, chela; Ar, rostrum; Aa, abdominal append- 
ages. The letters c, r and a apply to the same parts in each 
figure on the plates. 

lalate iy Kies, A, B,C, D, E, H, J and K are taken trom 
first-iorm males. Figs. F, G, I and L are taken from second- 
form males. 

In Plates II., Figs. M, O, P, QO and R are taken from first- 
form males. Fig. N, from a second-form male. 


Plate III. 


Figs. At to As inclusive show a developmental series of 
the first pair of abdominal appendages of the male C. gracilis. 

Fig. At, from an individual 23 mm. in length. 

Fig. A2, from an individual 27 mm. in length. 


(51) 


Fig. A3, from an individual 33 mm. in length. 

Fig. A4, from an individual 40 mm. in length. 

Fig. As, from an individual 67 mm. in length. 

Figs. Br to B8 inclusive show a developmental series of 
the annulus ventralis of the female C. gracilis. 

Fig. B1, from an individual 20 mm. in length. 

Fig. B2, from an individual 23 mm. in length. 

Fig. B3, from an individual 27.5 mm. in length. 

Fig. B4, from an individual 30 mm. in length. 

Fig. Bs, from an individual 35 mm. in length. 

Fig. B6, from an individual 36 mm. in length. 

Fig. B7, from an individual 50 mm. in length. 

Fig. B8, from an individual 60 mm. in length. 

Fig. C1 — Hand (natural size) from C. whitmam. 

Fig. C2— First pair of abdominal appendages (1%) of 
second-form male C. whitmani. 

Figs. D1 to D3 inclusive show chela, rostrum and first pair 
of abdominal appendages of first-form males of the species 
C. mmunis. 

Fig. D1 —c, left chela, showing characteristic notch (n) 
near the ‘base of the movable finger; 17, typical C. wmmunis ros- 
trum; a, first pair of abdominal appendages. 

Fig. D2—c, right chela without characteristic notch near 
base of movable finger; 7, rostrum, not noticeably different from 
the rostrum shown in Fig. D1; a, first pair of abdominal 
appendages. 

Fig. D3 —c, right chele, showing characteristic notch (n) 
near base of movable finger; c, left chela, without notch near 
base of movable finger and smaller than the right chela; 7, ros- 
trum, distinctly angled at the base of acumen; a, first pair of 
abdominal appendages. 

Fig. E1 — Hand from a first-form male 71 mm. in length. 

Fig. E2— Hand from a second-form male 71.5 mm. in 
length. ; 

Fig. k3 — Hand from a female 80 mm. in length. 


Plate IV. 


The figures in Plate IV. show comparisons between the 
reproductive organs and first pair of abdominal appendages in 
first-iorm and second-form males of C. wirtls. All the repro- 
ductive organs shown are drawn from crayfish which were 
examined in June. Y 

Fig. A— Reproductive organs from a second-form male 


(52) 


without chelz. #, testes, the three lobes slender, without 
secondary lobules; v, vasa deferentia, long and convoluted. 

Fig. At — First pair of abdominal appendages taken from 
the same individual as the reproductive organs shown in Fig. A. 
They are thick, have narrow bases and closely approximated 
tips. 

Fig. B — First pair of abdominal appendages of a second- 
form male without chele. Appendages are shown from the 
ventral side. The bases are narrow and do not meet in the 
median line. 

Fig. Br — Reproductive organs taken from the same indi- 
_ vidual as the appendages shown in Fig. B. ¢, testes. The con- 
nection between the lobes is very short and the two anterior 
lobes are only imperfectly separated; uv, the vasa deferentia are 
short and unconvoluted. 

Fig. C— First pair of abdominal appendages of a second- 
form male with chele. The bases are broad and the tips widely 
gaping. 

Fig. D — Reproductive organs of a large first-form male. 
t, testes. The lobes are large and full, and are distinctly sepa- 
rated, anterior lobes unsymmetrical; v, vasa deferentia, much 
convoluted. 

Figs. EK, F and G are all taken from the same individual, 
a large male with chele. 

Fig. E, represents a side view of the first pair of abdominal 
appendages after the first moult. 

Fig. F represents a ventral view of the same appendages, 
drawn in natural position. Note the closely approximated 
bases. 

Fig. G represents the same pair of appendages just after 
second moult, showing transformation from second-form into 
first-form. 

Fig. H — Two views of a first abdominal appendage of a 
second-form male with chele. ! 

Fig. I — Typical reproductive organs of a first-form male. 
Lobes of the testes (t) widely separated and lobulated. 

Fig. K—Chela (natural size) from a second-form male 
after it had moulted three successive times into second-form. 
Almost the entire growth had taken place within a single month. 


Plate Vi: 


Fig. A — Life-size drawing of C. aversii. 
Fig. B— Life-size drawing of C. whitmani. 


(53) 


Plate VI. 


A series of figures reproduced from photographs of crayfish 
belonging to the species C. rusticus. Figures are about two- 
thirds natural size. These photographs represent a graded 
series oi the species, showing variations in shape of rostrum and 
chelz, in breadth of areola and in relative lengths of cephalo- 
thorax and abdomen. 

Fig. 1 — Male C. rusticus (according to Faxon C. neglectus). 

Fig. 2— Male C. rusticus (according to Faxon C. neglectus). 

Fig. 3— Male C. rusticus. Note that the differences 
between Fig. 3 and Figs. 1 and 2 are not so great as are often 
seen between individuals that are constantly classed as the 
same species; e. g., in C. wirilis. 

Fig. 4— Female C. rusticus. Body contour closely resem- 
bles Figs. 1 and 2. Hands short-and thick, as is usual in females 
of any species of Cambarus. 

Fig. 5 — Male, C. rusticus. The chief difference between 
this figure and Figs. 1 and 2 lies in the rostrum, a feature which 
is found to be very inconstant in any species. 

Fig. 6 — Male, C. rusticus. Rostrum from the rostra shown 
in Figs. 1 and 2, but not more different than from the rostra 
shown in Figs. 4 and 5. 

Fig. 7— Male, C. rusticus. Rostrum and chele both dif- 
ferent from the rostrum and chelz shown in preceding figures. 


LIBRARY 
OF THE 
UNIVERSITY of ILLINOIS 


Crayfish of Missouri. Plate E. 


M. Steele, del. 


Crayfish of Missouri. Plate 1, 


Vs 


M. Steele, del. 


LIBRARY 
OF THE 
UNIVERSITY of ILLINOIS 


Crayfish of Missouri. Plate III. 


M. Steele, del. 


Plate IV. 


issouri. 


Crayfish of M 


M. Steele, del. 


Notre To THE READER: Plate V. is omitted but Fig. A is 
printed as Fig. 14 0n Plate VI. Fig. B is not given. 


LIBRARY 
OF THE 
UNIVERSITY of ILLINOIS 


Crayfish of Missouri. Pilate Vit. 


— : 
Cayersti. Re lg 
7. . af 


M. Steele photo figs. 1-13. H. Ayers, del. fig. 14. 


haar: 
eas 


iat 
‘ 


‘ 


aye 


Nee eta 


1153398 


